Here is my graph of the corners measurement...
corners.jpg
I ran this with REW & the sub calibrated to 80 hz baseline, using the REW pink noise output.
to me, it sure looks like the axial length 19, 38 & 57 hz modes are all showing, along with the axial width 44 hz mode. But what are the sharp valleys in there - they sure look like nulls to me, around 56, 77 (shouldn't that be a peak instead, from the axial length modes?!).
Is it possible to get nulls in a corner? Do you think that's what those are, those sharp valleys, or are those just what it's supposed to be at, and the modes are so pronounced that the parts in between appear to be valleys...
Based on these mode measurements, I had wanted to put the subs at the 1/3 & 2/3 positions along the length wall, based on a suggestion from Ed Mullen, but when I did that and mic'ed the corner again, it didn't really eliminate the 19 hz bulge, and I still got a 31-32hz null, coming out of nowhere...will have to redo that measurement and post the graph to show you.